What is the 5-day window during which COVID-19 is most transmissible?

People infected with SARS-CoV-2, the virus that causes COVID-9, are most contagious two days before symptoms appear and three days after onset (Reuters/Toya Sarno Jordan/file photo)

When a person learns that someone close or known to whom he was, the disease has been confirmed covid-19, He wonders if he was injured too. And must Do a repeat PCR test in 7 days to confirm the diagnosis.

But you’ll also end up wondering if you’re at risk for infection. But what is this range of days?

A new study co-led by a researcher at Boston University School of Public Health (USA) finds that People infected with SARS-CoV-2, the virus that causes COVID-9, are most contagious two days before symptoms appear and three days after symptoms appear. investigation that Published in the journal JAMA Internal Medicine, It also reveals that infected people are more likely to be asymptomatic if they contract the virus from an initial case (the first infected person in an outbreak) who is also asymptomatic.

Nearly 9,000 close contacts of primary cases were studied in China's Zhejiang Province from January 2020 to August 2020 (Reuters/Ali Song)
Nearly 9,000 close contacts of primary cases were studied in China’s Zhejiang Province from January 2020 to August 2020 (Reuters/Ali Song)

In previous studies, viral load was used as an indirect measure of transmission. We wanted to see if the results of these previous studies, which show that Cases of COVID-19 are most prevalent a few days before and after symptoms appear, It can be confirmed by observing secondary cases among close contacts”, explains the doctor. Leonardo Martinez Co-director of the study.

Martínez and colleagues conducted contact tracing and roughly studied the transmission of COVID-19 9,000 close contacts of primary cases in China’s Zhejiang Province from January 2020 to August 2020. Close contacts included household contacts (defined as individuals who live in the same home or eat together), co-workers, people in hospitals, and passengers in shared vehicles.

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Researchers followed infected individuals for at least 90 days after initial positive test results to distinguish between asymptomatic and pre-symptomatic cases. Among the individuals identified as primary cases, 89 percent had mild or moderate symptoms, only 11 percent were asymptomatic, and none developed severe symptoms.

Close contacts were more likely to contract COVID-19 than the primary infected individual (EFE/Salas/File)
Close contacts were more likely to contract COVID-19 than the primary infected individual (EFE/Salas/File)

Family members of the primary cases, as well as people who were exposed to the primary cases several or more times, had higher infection rates than other contacts. But regardless of these risk factors, Close contacts were more likely to contract the COVID-19 virus than the primary infected person if they were exposed to it before or shortly after the individual developed noticeable symptoms.

“Our results indicate that The timing of exposure relative to the symptoms of the initial case is important for transmission, and this knowledge provides further evidence that rapid tests “Quarantining after someone feels sick is a critical step in controlling the epidemic,” says Dr. Martinez.

Compared to individuals with mild and moderate symptoms, Initial asymptomatic individuals were less likely to transmit COVID-19 to close contactsBut if it does, contacts are less likely to develop noticeable symptoms. “This study also underscores the need for vaccination, which reduces clinical severity among people who develop COVID-19,” Martinez says.

It is in the window period where the possibility False negatives. If the test is done in the first days of infection/infection The test result may be negative; however, This finding does not rule out infection. It may be that the immune system has not yet produced enough defenses to be detected by the test performed.

It is in the window period where the possibility of false negatives appears.  REUTERS / Shannon Stapleton / File Photo
It is in the window period where the possibility of false negatives appears. REUTERS / Shannon Stapleton / File Photo

considering the window period so what Each immune system is different and works differently, it is recommended at that time, as mentioned at the beginning, to do the PCR test when symptoms appear or when close contact is considered, Because it can be an infected person without symptoms. Use an antibody test when you’ve been very suspicious of having the disease for a while.

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Aileen Morales

"Beer nerd. Food fanatic. Alcohol scholar. Tv practitioner. Writer. Troublemaker. Falls down a lot."

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